The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In order to make resistant and light structural members, in particular for the aeronautical field, it is known to prepare a dry fabric preform comprising for example carbon fibers, which is impregnated with a resin, in particular by an injection method called “RTM” (Resin Transfer Molding).
There is thus obtained, after baking to polymerize the resin, a member comprising fibers whose density and orientation are locally adjusted, in order to obtain mechanical resistance features adapted for the stresses applied to this part.
In particular, it is possible to make, by means of this technique, skin-shaped parts bent about an axis such as axisymmetric shrouds and including at least one circumferential stiffener giving rigidity to this skin: such a skin may be used, in particular in manufacturing an aircraft engine nacelle.
In some cases, the stiffening function is ensured by a member having a constant cross section substantially resembling an omega (“Ω”), comprising a core (the round portion of the omega) and a sole (the extended base of the section of the omega).
For making the assembly formed by the bent skin to be stiffened and the omega-shaped stiffener, it is known to separately make the skin and the stiffener which are pre-baked, then assembled by a mechanical connection or bonding.
It is also known to make one of these members by pre-baking, then to set up the dry preform of the second member on this first member in order to carry out its impregnation then its baking, which assembles them at the same time.
Finally, it is known to make two separate preforms, with simultaneous impregnation and baking of these two preforms put into position relative to each other.
However, these solutions do not provide a strong binding between the core and the sole of the omega-shaped stiffener. Therefore, there is obtained a reduced mechanical aspect, with an adhesion failure risk by peeling in case of traction on the core or on the sole of the stiffener.
Alternatively, the stiffener may be incorporated into the skin to be stiffened by hand-made drapings of flat fabrics. However, this operation requires a significant workforce, resulting in additional costs. Furthermore it requires many fabric cuttings, and the orientation of fibers is not optimized.